The present invention relates to a technique for holding a substrate, such as a mask or a reticle, a semiconductor wafer, and a glass plate, for use with a semiconductor exposure apparatus.
A conventional substrate holder holds a reticle and a wafer in a semiconductor exposure apparatus through one surface of the substrate, such as its bottom or top surface, or its front or rear surface. For example, as shown in Japanese Patent Applications, Publication Nos. 9-270383, 2000-349022 and 2001-156151, an exposure stage holds a bottom surface of a substrate, and a substrate feeder for feeding a substrate to and from the stage holds one of the top and bottom surfaces of the substrate. While a substrate can be held longitudinally or perpendicularly, as disclosed in Japanese Patent No. 2,862,632, even this case allows the stage and substrate feeder to hold one surface of the substrate. In Japanese Patent No. 2,862,632, both the exposure stage and the substrate feeder for feeding the substrate to and from the stage hold the rear surface of the substrate.
If it is assumed, as disclosed in Japanese Patent Application, Publication No. 9-270383 and Japanese Patent No. 2,862,632, that the feeder's substrate holding member and the stage's substrate holding member hold the same plane of the substrate, the holding areas are restrained so as to avoid mutual interference. As a result, it becomes difficult to meet recent demands for high feed speed and increased holding power. In addition, it is difficult to correct a tilt that can occur between the feeder and the stage, and the correction requires an actuator-driven correction mechanism.
On the other hand, if it is assumed, as disclosed in Japanese Patent Application, Publication No. 2000-349022, that the feeder's substrate holding member and the stage's substrate holding member hold different planes of the substrate, the substrate holding members of the feeder and stage do not suffer from mutual restraints of the holding areas. In addition, the tilts between them are easily corrected without using the actuator. Instead, this case requires a structure that allows for distortions, such as a flat spring structure. As a result, it is difficult to maintain the surface position or posture of the substrate due to its elasticity when they singularly (by themselves) hold the substrate.
Japanese Patent No. 2,862,632 discloses an example of a tilt correction mechanism, although holding the same plane of the substrate. If the attraction power disappears by the substrate holding member when the top surface of the substrate is being attracted and held, the substrate drops and gets damaged. Japanese Patent Application, Publication No. 2001-156151, discloses a measure to prevent dropping of the substrate due to the reduced attraction power.